The invention relates to a seal fitting and its method of installation within high pressure and temperature environments such as steam turbines and the like.
Instrumentation internal to steam cooled nozzles (pressure vessels) require an exit sealing fitting capable of sustaining high pressure. In such applications, a large number of instrumentation leads must be able to exit from the interior to the exterior of the pressure vessel through the fitting yet the fitting must be small enough as to not cause interference problems when installing the fittings to the pressure vessel.
Prior art seal fittings have utilized a commercially available xe2x80x9cLavaxe2x80x9d (Natural Magnesium Silicate) sealant. The Lava seal is a compressed powder composition, which is compacted internal to the fitting at assembly to form a seal around the leads within the interior of the fitting body.
The Lava seal, however, does not always seal the leads adequately, often allowing fluid leakage through the fitting to the exterior of the pressure vessel. Moreover, the lava seal fitting allows for only one lead per slot in the fitting thereby necessitating the use of multiple fittings. If more than one lead per slot is used with conventional lava fittings then the leakage problems are exacerbated, as the compressed powder composition cannot be tightly fitted against and around multiple leads within a single slot. The overall fitting size has also proven to be too large, and frequently has to be modified at the assembly stage to prevent interference.
The major components of assembled Lava seal 50, are shown in FIGS. 1-3, to include housings 53 and 54, driver 60, seat 61 and sealant 62. As generally shown in FIG. 3, driver 60, seat 61 and sealant 62 have a slotted profile when being viewed from one end, and for the reasons given above only one lead can be positioned in each slot 63 of these components. During assembly, driver 60 is used to compress the powder composition placed within housings 53 and 54 and between driver 60 and sealant 62, into close proximity and sealing contact around each lead disposed in each of the slots 63 of sealant 62.
FIG. 4 shows an installed Lava seal 50 in which the housing had to be modified by cutting side surface 64 so that it could be installed in tight conditions.
The present invention overcomes the problems associated with prior art seal fittings.
The present invention employs a low profile fitting body that is approximately xc2xd the height of prior art fittings, thereby eliminating most interference issues. The seal fitting of the present invention includes internal pieces which allow for more than one lead per slot, at least doubling the amount of instrumentation exiting the pressure vessel for each fitting.
Finally, the brazed fitting provides excellent sealing between leads in each slot, and from the slots to the fitting body inner diameter wall. The present invention also provides adequate assembly clearance between internal parts and the fitting body.
In summary, the present invention provides the structural soundness to meet pressure limits, and provides exit for at least twice as many sensor leads as was previously possible, yet in an overall smaller size profile fitting.